1. Field of the Invention
This invention relates to an automatic stamper exchange device and an injection molding apparatus. More particularly, it relates to an automatic stamper exchange device having the function of automatically mounting and dismounting a stamper and an injection molding apparatus employing such exchange device.
2. Background of the Invention
There has been proposed an optical disc having a disc substrate formed of a synthetic resin having light transmitting properties, such as acrylic resin or polycarbonate resin, and a recording layer formed thereon, in which light is radiated as an extremely small light spot on the recording layer for high-density recording of information signals, such as music or picture signals, reading out the recorded information signals and rewriting the recorded information signals. Such optical disc is wisely used in a recording and/or reproducing system for audio or video signals or in an external storage device for an electronic computer.
Such optical disc has a transparent disc substrate having a pattern of lands and recesses, such as pits or grooves, representing information signals, formed thereon, a reflective film, as a recording film, such as a thin film of metal, such as aluminum, formed on the disc substrate, and a protective film for protecting the reflective film against the moisture or oxygen in the atmosphere, formed on the reflective film. For reproducing the information recorded on the optical disc, the light beam is radiated on the pits from the side of the transparent substrate and the return light detected for detecting the information.
The disc substrate of the optical disc is formed by setting a stamper having pre-set information signals recorded as a pattern of fine lands and recesses, or so-called pits and grooves, set on a metal mold of an injection molding machine, and by injecting a heated and molten resin material, such as polycarbonate resin, into the inside of the metal mold. On a surface of the molded disc substrate, which is to be a signal recording surface, is formed an aluminum reflective film, such as by vapor deposition or sputtering, and a protective film of, for example, a UV curable resin, is formed thereon.
In the fabrication of the optical discs, when a pre-set number of the disc substrates of the optical discs, each having a set of information signals recorded thereon, are completely produced, optical discs each having another set of information signals recorded thereon are produced as a next process. Thus it becomes necessary to exchange a stamper for a new one when the disc substrates of the optical discs having one set of the information signals recorded thereon have been completed, in order to produce the disc substrate of the optical disc having another set of information signals recorded thereon.
Up to now, stamper exchange was carried out entirely by man power. For example, when a pre-set number of disc substrates has been fabricated, an operator introduces a rod-shaped jig into a center hole in the stamper mounted on the metal mold for dismounting the stamper from the metal mold. A new stamper is then mounted on the metal mold using a similar jig.
Since the stamper exchange is performed by a manual operation by an operator, it may occur that the operator may inadvertently touch the signal recording surface of the stamper with his or her finger during the exchange operation, thereby contaminating or damaging the information recording surface. If the stamper should become defective, the disc substrates of the optical disc duplicated from the stamper become defective in their entirety, thus rendering it impossible to correctly read out playback signals and lowering the yield or operational reliability.
On the other hand, both the used-up stampers and the new stampers are housed by the operator in stamper casings and stored in the housing unit. Consequently, since it becomes necessary to take out the stampers from the stamper casing, tactile contact with the stamper occurs unavoidably.